Ingrid Ukstins Peate

Re-evaluating the geochronology of the Permian Tarim magmatic province: implications for temporal evolution of magmatism

The Permian Tarim magmatic province has 118 published ages, ranging from 358 to 205 Ma, but the timing of mafic magmatism is not well constrained. We report two new secondary ion mass spectrometry U–Pb zircon dates on the Halahatang trachydacite and Wajilitag olivine clinopyroxenite, which are 287.2 ± 2.0 Ma and 283.2 ± 2.0 Ma, respectively. The trachydacite overlies the uppermost basalt and constrains the latest eruption age of basalt in northern Tarim. The latter is the first high-resolution date for the Wajilitag mafic layered intrusion. By screening all published ages, we identified 22 robust ages, ranging from 290.9 ± 4.1 to 261.7 ± 1.8 Ma. The robust ages together with our new data reveal a protracted period of mafic magmatism at c. 283 and c. 267 Ma. Silicic magmatism occurred from 291 to 272 Ma. Although the current known volume of Tarim basalt is too small to qualify as a large igneous province, the eroded and intrusive components, as well as pyroclastic deposits and silicic lavas, may increase the estimated volume. Further work is required to refine the duration of magmatism and the volume estimate of the province. Supplementary material: A list of all the published dates, raw data of published 40Ar–39Ar dates, raw data of published U–Pb dates, published geochemistry data used for calculation and complete details of the data evaluation are available at http://www.geolsoc.org.uk/SUP18862.

The significance of the contemporaneous Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism

Abstract: The relationships between meteorite impact craters, flood basalt volcanism and sudden environmental perturbation on Earth have been debated extensively. We present only the second example of contemporaneous meteorite impact and flood basalt volcanism: the 17 km diameter Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism. The new precise 40Ar/39Ar age of 29.71 ± 0.48 Ma for Logoisk is coincident with the acme of flood volcanism. We argue that at least one crater the size of Logoisk is likely to form during the emplacement of a flood volcanic province, and that contemporaneity of impacts and flood volcanism was the norm. The absence of a biotic effect from the combined Logoisk–Afro-Arabian volcanism we attribute to the magnitude of these combined events, which are both significantly smaller than the other known example of the Chicxulub impact event and the Deccan Traps flood volcanism. Supplementary material: 40Ar/39Ar data are available at http://www.geolsoc.org.uk/SUP18329.